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+A Thrift SASL message shall be a byte array of one of the following forms:
+
+| 1-byte START status code | 1-byte mechanism name length | variable length mechanism name | 4-byte payload length | variable-length payload |
+| 1-byte status code | 4-byte payload length | variable-length payload |
+
+The length fields shall be interpreted as integers, with the high byte sent
+first. This indicates the length of the field immediately following it, not
+including the status code or the length bytes.
+
+The possible status codes are:
+
+0x01 - START - Hello, let's go on a date.
+0x02 - OK - Everything's been going alright so far, let's see each other again.
+0x03 - BAD - I understand what you're saying. I really do. I just don't like it. We have to break up.
+0x04 - ERROR - We can't go on like this. It's like you're speaking another language.
+0x05 - COMPLETE - Will you marry me?
+
+The Thrift SASL communication will proceed as follows:
+
+1. The client is configured at instantiation of the transport with a single
+underlying SASL security mechanism that it supports.
+
+2. The server is configured with a mapping of underlying security mechanism
+name -> mechanism options.
+
+3. At connection time, the client will initiate communication by sending the
+server a START byte, followed by a 1-byte field indicating the length in bytes
+of the underlying security mechanism name that the client would like to use.
+This mechanism name shall be 1-20 characters in length, and follow the
+specifications for SASL mechanism names specified in RFC 2222. This mechanism
+name shall be followed by a 4-byte, potentially zero-value message length word,
+followed by a potentially zero-length payload. The payload is determined by the
+output byte array of the underlying actual security mechanism, and will be
+empty except for those underlying security protocols which implement the
+optional SASL initial response.
+
+4. The server receives this message and, if the mechanism name provided is
+among the set of mechanisms this server transport is configured to accept,
+appropriate initialization of the underlying security mechanism may take place.
+If the mechanism name is not one which the server is configured to support, the
+server shall return the BAD byte, followed by a 4-byte, potentially zero-value
+message length, followed by the potentially zero-length payload which may be a
+status code or message indicating failure. No further communication may take
+place via this transport. If the mechanism name is one which the server
+supports, then proceed to step 5.
+
+5. The server then provides the byte array of the payload received to its
+underlying security mechanism. A challenge is generated by the underlying
+security mechanism on the server, and this is used as the payload for a message
+sent to the client. This message shall consist of an OK byte, followed by the
+non-zero message length word, followed by the payload.
+
+6. The client receives this message from the server and passes the payload to
+its underlying security mechanism to generate a response. The client then sends
+the server an OK byte, followed by the non-zero-value length of the response,
+followed by the bytes of the response as the payload.
+
+7. Steps 5 and 6 are repeated until both security mechanisms are satisfied with
+the challenge/response exchange. When either side has completed its security
+protocol, its next message shall be the COMPLETE byte, followed by a 4-byte
+potentially zero-value length word, followed by a potentially zero-length
+payload. This payload will be empty except for those underlying security
+mechanisms which provide additional data with success.
+
+If at any point in time either side is able to interpret the challenge or
+response sent by the other, but is dissatisfied with the contents thereof, this
+side should send the other a BAD byte, followed by a 4-byte potentially
+zero-value length word, followed by an optional, potentially zero-length
+message encoded in UTF-8 indicating failure. This message should be passed to
+the protocol above the thrift transport by whatever mechanism is appropriate
+and idiomatic for the particular language these thrift bindings are for.
+
+If at any point in time either side fails to interpret the challenge or
+response sent by the other, this side should send the other an ERROR byte,
+followed by a 4-byte potentially zero-value length word, followed by an
+optional, potentially zero-length message encoded in UTF-8. This message should
+be passed to the protocol above the thrift transport by whatever mechanism is
+appropriate and idiomatic for the particular language these thrift bindings are
+for.
+
+If step 7 completes successfully, then the communication is considered
+authenticated and subsequent communication may commence.
+
+If step 7 fails to complete successfully, then no further communication may
+take place via this transport.
+
+8. All writes to the underlying transport must be prefixed by the 4-byte length
+of the payload data, followed by the payload. All reads from this transport
+should read the 4-byte length word, then read the full quantity of bytes
+specified by this length word.
+
+If no SASL QOP (quality of protection) is negotiated during steps 5 and 6, then
+all subsequent writes to/reads from this transport are written/read unaltered,
+save for the length prefix, to the underlying transport.
+
+If a SASL QOP is negotiated, then this must be used by the Thrift transport for
+all subsequent communication. This is done by wrapping subsequent writes to the
+transport using the underlying security mechanism, and unwrapping subsequent
+reads from the underlying transport. Note that in this case, the length prefix
+of the write to the underlying transport is the length of the data after it has
+been wrapped by the underlying security mechanism. Note that the complete
+message must be read before giving this data to the underlying security
+mechanism for unwrapping.
+
+If at any point in time reading of a message fails either because of a
+malformed length word or failure to unwrap by the underlying security
+mechanism, then all further communication on this transport must cease.